Variable reflection acoustic wall system by active sound radiation

In the acoustic design of special spaces, such as studios, it may be required to realize diffuse reflection from a specific surface of a wall. Moreover, this requirement often changes with time or situation. In this research study, a new acoustic wall system, which has the potential to cope with such strict requirements, is proposed. The proposed system can vary the reflection characteristics by radiating additional sound from a source located behind the absorbing material. Therefore, if sound is not emitted from the source, it is possible to use the system as a mere sound absorbing material. This system can be used as a rigid wall, provided sound of equal amplitude to the incident sound is emitted from the source. Furthermore, a trial was carried out to make the characteristics of radiated sound being diffuse by using appropriate devices. Several models are proposed and the fundamental characteristics such as directivity were examined. The results show the possibilities for realizing uniform reflection directivity and variable absorption characteristics.